U.S. patent number 10,858,020 [Application Number 15/817,280] was granted by the patent office on 2020-12-08 for systems and methods for using a railroad rail as radiating element for transmitting wireless communications signals.
This patent grant is currently assigned to Meteorcomm LLC. The grantee listed for this patent is Meteorcomm LLC. Invention is credited to Arun Naidu.
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United States Patent |
10,858,020 |
Naidu |
December 8, 2020 |
Systems and methods for using a railroad rail as radiating element
for transmitting wireless communications signals
Abstract
A railroad communication system includes a radio transmitter for
generating radio communications signals and a length of railroad
rail coupled to the radio transmitter. The length of rail is
disposed on a set of nonconductive railroad ties to form a
transmission line for radiating the radio communications signals to
a radio receiver in a vicinity of the length of railroad rail.
Inventors: |
Naidu; Arun (Woodinville,
WA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Meteorcomm LLC |
Renton |
WA |
US |
|
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Assignee: |
Meteorcomm LLC (Renton,
WA)
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Family
ID: |
54334032 |
Appl.
No.: |
15/817,280 |
Filed: |
November 19, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20180072334 A1 |
Mar 15, 2018 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14503981 |
Oct 1, 2014 |
9840260 |
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61983769 |
Apr 24, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B61L
15/0027 (20130101); B61L 3/227 (20130101); B61L
3/125 (20130101); B61L 15/0072 (20130101); B61L
27/00 (20130101) |
Current International
Class: |
B61L
3/22 (20060101); B61L 15/00 (20060101); B61L
3/12 (20060101); B61L 27/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Office Action received in Canadian Application No. 2,888,557 dated
Jun. 3, 2016, 4 pages. cited by applicant .
WireYourOwnHouse.com, "Grounding the Service,"
http://wireyourownhouse.com/panel/grounding.html, 2010, 5 pages.
cited by applicant .
Jarrett, K. W. et al., "Traditional Transmission Media for
Networking and Telecommunications,"Coaxial Cable, Oct. 2007, 3
pages. cited by applicant.
|
Primary Examiner: Le; Mark T
Attorney, Agent or Firm: Hubbard Johnston PLLC
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a Continuation of U.S. patent application Ser.
No. 14/503,981 filed Oct. 1, 2014, which this application claims
the benefit of U.S. Provisional Application No. 61/983,769, filed
Apr. 24, 2014. The above identified applications are incorporated
by reference herein.
Claims
What is claimed is:
1. A railroad communication system comprising: a wayside Positive
Train Control (PTC) radio transmitter for communicating PTC
messages through radio communications signals; and a length of
heavy freight railroad rail coupled to the wayside Positive Train
Control (PTC) radio transmitter and disposed on a set of
nonconductive railroad ties to form a transmission line for
radiating the radio communications signals with an electric field
sufficient for communication of RF signals with enough strength at
the height of a locomotive PTC antenna mounted on top of a
locomotive for reliable transmission of PTC messages.
2. The railroad communication system of claim 1, wherein the
electric field has a strength of -6 dBV/m.
3. The system of claim 1, further comprising a radio receiver
carried by a railroad worker in the vicinity of the length of
railroad rail.
4. The system of claim 1, wherein the wayside Positive Train
Control (PTC) radio transmitter is coupled to the length of heavy
freight railroad rail through a track radio transmitter.
5. The system of claim 4, wherein the track radio transmitter
receives signals with PTC messages from a PTC radio system.
6. The system of claim 1, further comprising a PTC radio receiver
disposed on the locomotive and connected with the PTC antenna.
7. The system of claim 1, wherein the length of rail comprises a
portion of a rail block separated from an adjacent rail block by an
insulator.
8. The system of claim 1, wherein the length of rail comprises a
portion of a continuous rail.
9. A method for radio communication in a railroad system
comprising: coupling a wayside Positive Train Control (PTC) radio
transmitter to a length of railroad rail disposed on a plurality of
railroad ties to form a transmission line; and transmitting PTC
messages from the wayside PTC radio transmitter to a radio receiver
on a locomotive by transmitting communication signals through the
length of railroad rail to an antenna mounted on top of a
locomotive.
10. The method of claim 9, wherein transmitting radio
communications signals comprises transmitting the PTC messages to a
radio receiver associated with personnel working in the vicinity of
the length of railroad rail.
11. The method of claim 10, wherein transmitting messages to a
radio receiver associated with personnel working in the vicinity of
the length of railroad track comprises transmitting warning
messages.
12. The method of claim 9, wherein the transmitting of radio
communications signals from the length of railroad rail comprises
transmitting radio communications signals to a train in the
vicinity of the length of rail.
13. The method of claim 9, wherein coupling the wayside PTC radio
transmitter to a length of railroad rail comprises coupling the
wayside PTC radio transmitter through a track radio transmitter to
the length of railroad rail.
14. The method of claim 9, wherein coupling the wayside PTC radio
transmitter to a length of railroad rail comprises coupling the
wayside PTC radio transmitter to a length of railroad rail through
a coaxial cable.
15. The method of claim 14, wherein coupling the wayside PTC radio
transmitter to a length of railroad rail through a coaxial cable
comprises: coupling a center conductor of the coaxial cable to a
bolt disposed through an aperture through a web of the length of
railroad rail; and coupling a shield of the coaxial cable to a
grounding rod.
16. The method of claim 14, wherein coupling the wayside PTC radio
transmitter to a length of railroad rail through a coaxial cable
comprises: coupling a center conductor of the coaxial cable to a
web of the length of rail with a conductive adhesive; and coupling
a shield of the coaxial cable to a grounding rod.
17. The method of claim 9, wherein the radio communications signals
are radiated with an electric field having a strength of -6
dBV/m.
18. The method of claim 9, wherein the rails are heavy freight
rails positioned above the ground by ties.
Description
FIELD OF INVENTION
The present invention relates in general to the wireless
transmission of communications signals, and in particular to
systems and methods for using a railroad rail as a radiating
element for transmitting wireless communications signals.
BACKGROUND OF INVENTION
Railroads use a number of different wireless communications
systems, including radios, in their operations. For example, radio
communications between locomotives and waysides is an important
component of the Positive Train Control (PTC) system being
implemented in the United States. In addition, railroads rely on
radios to communicate with personnel out in the field, including
those working in the proximity of active railroad tracks. Hence
improving railroad radio communications capabilities is an
important factor in ensuring safe and efficient railroad
operations.
SUMMARY OF INVENTION
The principles of the present invention are generally embodied in
systems and methods in which a conventional railroad rail is used
to carry and radiate radio frequency (RF) signals at one or more
frequencies to nearby radio receivers. Among other things, these
systems and methods support the transmission of messages to alert
rail side workers of an approaching train, transmit positive train
control (PTC) messages between locomotives and wayside radio units,
as well as provide a radio frequency transmission structure
suitable for other railway radio communications applications.
One particular representative embodiment of the principles of the
present invention is a railroad communication system, which
includes a radio transmitter for generating radio communications
signals and a length of railroad rail coupled to the radio
transmitter. The length of rail is disposed on a set of
nonconductive railroad ties to form a transmission line for
radiating the radio communications signals to a radio receiver in a
vicinity.
Among other things, the present principles take advantage of the
existing railroad infrastructure as a component in an extensive
communications system that is critical for maintaining efficient
railroad operations and safety. Advantageously, these principles
can be applied to rail blocks having rails separated by insulators
for maintaining DC communications or for continuous rail systems.
Existing radios, such as those used in the PTC system, can suitably
be used to generate the transmit signals, as well as receive
signals radiated from the rail.
BRIEF DESCRIPTION OF DRAWINGS
For a more complete understanding of the present invention, and the
advantages thereof, reference is now made to the following
descriptions taken in conjunction with the accompanying drawings,
in which:
FIG. 1 is a conceptual diagram of a small section of a microstrip
structure commonly used as a transmission line for carrying
electrical signals;
FIG. 2 is a perspective view of a small section of conventional
railroad track, including a portion of one of a pair of parallel
rails and their associated ties;
FIG. 3 is a cross-sectional view of a section of conventional
railroad rail;
FIG. 4 is a perspective view illustrating the insulators between a
pair of conventional rails of a small section of a conventional
railroad track;
FIG. 5 illustrates the radiated signal strength along a
representative section of railroad track operating as a radiator
according to the principles of the present invention;
FIG. 6 illustrates a representative application of the present
inventive principles in which a radio transmits a wireless warning
signal using a railroad rail as a radiating element to another
radio carried by a worker working trackside in the vicinity of the
railroad rail;
FIG. 7 illustrates another representative application of the
inventive principles in which a wayside radio transmits wireless
signals using a railroad track as a radiating element to another
radio on a locomotive on the railroad rail; and
FIG. 8 shows exemplary interconnection between an transmitting
radio and a railroad rail being used as a radiating element for
transmitting wireless signals.
DETAILED DESCRIPTION OF THE INVENTION
The principles of the present invention and their advantages are
best understood by referring to the illustrated embodiment depicted
in FIGS. 1-8 of the drawings, in which like numbers designate like
parts.
The structure formed by a conventional railroad sitting on a
conventional railroad tie is similar to that of a microstrip
transmission line, although the relative dimensions of the railroad
rail are much larger than that of the typical microstrip line used
in small-scale electrical systems, such as printed circuit boards.
As a result, a rail can be used as a transmission line for carrying
and radiating radio frequency signals at several different
frequencies. These signals could, for example, carry warning
messages to alert rail side workers of an approaching train,
transmit positive train control (PTC) messages from wayside radio
units to nearby locomotives, and carry similar signals needed for
implementing various other railway communications.
More specifically, FIG. 1 illustrates a conventional microstrip
structure 100 used as a transmission line for radio frequency (RF)
and microwave signals. In exemplary microstrip structure 100, a
microstrip 101, which a strip of conductive material having a width
W, a length I, and a thickness t, is separated from a ground plane
102 by a layer of dielectric 103 of thickness h.
For comparison, a small section of conventional railroad rail 200
is shown in FIG. 2, along with its cross-section in FIG. 3. Rail
200 includes a head 300, a base 301, and a web 302. A typical heavy
freight rail is about 2 23/32'' wide across head 300 (i.e., W=2
23/32'') and about 65/8'' tall, as measured from the bottom of base
301 to the top of head 300 (i.e., t=65/8''). As shown in FIG. 2,
the typical heavy freight rail is suspended over the ground by 7''
tall ties 201 (i.e., h=7''). Using these figures for W, t, and h
respectively, the characteristic impedance of a rail as microstrip
is approximately 180 Ohms.
A simulation was performed in which these rail dimensions were
entered into an Method of Moments electromagnetic simulation tool
and driven with a source signal at 220 MHz, which is the nominal
communications frequency used in the PTC system. Included in the
simulation was a 1/8'' gap with a Kevlar insulator 401 (FIG. 4),
typically used for electrically isolating adjacent track blocks
when the rail is used for DC signaling. (The principles of the
present invention are equally applicable to continuously welded
tracks, which use audio signaling detectors, which are not affected
by RF signals.)
FIG. 5 shows the simulated radiated signal strength along a length
of the track and demonstrates that an electric field (e:) of -6
dBV/m can be consistently achieved, which is well above the minimum
signal level requirements of current radio receivers. Under the
simulated conditions, the electrical field was found to be
sufficient to support communications with the handheld radios
carried by railroad workers within a nominal 1500 foot radius along
a nominal 1000 foot radiating length of track 200. (While the -6
dBV/m value for the electric field was determined through
simulation using the exemplary dimensions described above for the
rail and ties, the actual value for the electrical field strength
may vary in actual implementations, depending on such factors as
differences in rail head width, rail height, tie height,
transmitter power, and so on. Given the physical dimensions of the
track and ties, the transmitter power may accordingly be varied
depending on the desired size of the communications area
surrounding the radiating track. For example, depending on the
transmitter, the radial coverage of the electrical field could be
extended beyond the simulated 1500 foot nominal radius and/or the
length of the radiating section of track extended beyond the
simulated 1000 feet to a mile or more.)
This ability of the rail to radiate signals therefore
advantageously allows for the implementation of numerous
communication applications between devices in close proximity of
the rails. In other words, the rail becomes part of the
communications link between radios located near the rail and a
wireless aggregation radio located at wayside. Two exemplary
implementations are shown in FIGS. 6 and 7.
In FIG. 6, a wayside PTC radio 600 and an optional track radio 601
transmit messages to the radio receivers 602a and 602b carried
railroad workers in the vicinity of rail 200. These messages could
carry, for example, warnings about the approach of a train on the
track. PCT radio 600 and track radio 601, as well as the required
modulation and messaging protocols, could be, for example, those
described in U.S. Pat. Nos. 8,279,796, 8,340,056. 8,374,291, and
8,605,754, which are incorporated herein for all purposes. Optional
track radio 601 is preferably used when a different frequency,
modulation, or messaging protocol from that used by PTC radio 600
is desired.
In FIG. 7, a similar PTC radio 600 at a wayside is shown
transmitting PTC messages to a corresponding radio on a train
locomotive 700 using one of the rails 200 of the track as a
radiator. An electric field of -6 dBV/m advantageously provides
sufficient signal strength at the height of the locomotive 700 PTC
antenna for reliable message transmission.
A preferred interconnection between the PCT and/or track radios 600
and 601 shown in FIGS. 6 and 7 and the rail being used as a
radiator is shown in FIG. 8. In the embodiment shown in FIG. 8, a
coaxial cable 800 carries the RF signal transmitted by PTC radio
600, for the system shown in FIG. 7, or by track radio 601, for the
system shown in FIG. 6, to rail 200. The center conductor of
coaxial cable 800 couples to rail 200 through a bolt 801, which
preferably extends through an existing hole in web 302. In
alternate embodiments, conductive tape or conductive epoxy may be
used to couple the center conductor of coaxial cable 800 to rail
web 305 in lieu of bolt 801. The shield of coaxial cable 800 is
grounded through a ground rod 802 and a ground lead 803. In
alternate embodiments, different radio-to-rail interconnection
techniques may be used.
Although the invention has been described with reference to
specific embodiments, these descriptions are not meant to be
construed in a limiting sense. Various modifications of the
disclosed embodiments, as well as alternative embodiments of the
invention, will become apparent to persons skilled in the art upon
reference to the description of the invention. It should be
appreciated by those skilled in the art that the conception and the
specific embodiment disclosed might be readily utilized as a basis
for modifying or designing other structures for carrying out the
same purposes of the present invention. It should also be realized
by those skilled in the art that such equivalent constructions do
not depart from the spirit and scope of the invention as set forth
in the appended claims.
It is therefore contemplated that the claims will cover any such
modifications or embodiments that fall within the true scope of the
invention.
* * * * *
References